1. Field of the Invention
The present invention relates to an electrically rewritable non-volatile semiconductor storage device and a method of manufacturing the same.
2. Description of the Related Art
Recently, the number of bits (the number of transistors) tends to increase for the purpose of providing a larger amount of data to be written to one chip. This is achieved by shrinking the transistor size. On the other hand, for EEPROM using high voltage in writing or the like, HV-type transistors are essential that are durable for such high voltage. For example, non-volatile semiconductor devices includes two regions: a memory cell array arranging region, and a periphery region that surrounds the memory cell array arranging region, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2002-368141). The HV-type transistors are arranged in the periphery regions.
However, such HV-type transistors cannot be shrunken since it is difficult to decrease writing voltage. Furthermore, for example, the HV-type transistors are required as many as word lines because they are provided in row decoder circuits connected to the word lines, and hence the number of HV-type transistors cannot be reduced. Therefore, these HV-type transistors form bottlenecks for the entire chip, causing problems that the chip size cannot be shrunken.